Particulate adsorbent materials are used extensively for a variety of applications. Such materials act to adsorb, on the particle surfaces, one or more components of a fluid being processed. Granular carbon, alumina, silica, natural minerals and various catalysts are all examples of such materials.
After a period of use, particulate adsorbent materials lose their effectiveness as a result of the build-up of adsorbed materials on the surfaces and in the pores of the particles. The spent adsorbent material may, in some cases, be merely disposed of in a suitable landfill of the like. However, in many instances this is not practical or even possible, due to the high cost of the adsorbent material and/or environmental hazards. Accordingly, various processes have been developed for reactivating or regenerating such adsorbent materials.
So-called non-thermal process for the reactivation of particulate adsorbent materials include the use of biologic agents, solvents, reactive chemicals, and high vacuum. Some of these processes are very slow. Some do not accomplish a high degree of reactivation resulting in much shorter re-use life for the reactivated material. Some processes result in an effluent which is difficult or expensive to dispose of, and may constitute environmental hazards.
Several types of so-called thermal reactivation processes are used to reactivate particulate adsorbent material. Typically, such processes subject the material to a high temperature to volatilize or pyrolize adsorbed organic compounds. Such processes also may be accompanied by controlled chemical reaction with steam, carbon dioxide or oxygen. These types of processes may be carried out in multiple hearth vertical furnaces, rotary kilns, electrical furnaces, or fluidized bed furnaces. Such processes, however, because of the relatively large and expensive equipment used, often require removal of the contaminated adsorbent material to a specific site at which the thermal regeneration or reactivation furnace or kiln is located. Such processes are also extremely energy intensive, may be hazardous, and often result in substantial loss of the adsorbent material due to oxidation or other chemical reaction.
So-called steam reforming is a process which has been used to reactivate contaminated particulate adsorbent material. Alternatively, a non-condensible hot gas such as nitrogen, or mixtures of steam and other hot gases, may be used. In these processes, the hot steam or gas volatilizes the organics on the particulate adsorbent material, entraining them in the gas stream for subsequent condensation and recovery. Such processes, thus far, have typically not achieved a high enough level of removal of adsorbed compounds, resulting in substantially diminished effectiveness of the reactivated adsorbent materials.
An object of the present invention is to provide an improved process for reactivating particulate adsorbent materials, such as granular carbon.
Another object of the invention is to provide an improved reactivation process which is capable of being used "on site", obviating the need for shipping contaminated adsorbent materials.
Another object of the invention is to provide an improved reactivation process which is relatively low in cost of equipment, operation, and maintenance.
Another object is to advance the reactivation process by using reactive gases such as H.sub.2 and CO and steam-reform the heavier organics down in the pores of the particulates and clean the pores.
Another object of the invention is to provide an improved reactivation process wherein the loss of particulate adsorbent material is minimized, and wherein a high effectiveness of the reactivated material can be repeatedly achieved.
A further object of the invention is provide an improved reactivation process wherein optimum operating parameters can be readily established during the process.
Other objects of the invention will become apparent to those skilled in the art from the following description.